linux-kernel - Re: [PATCH 3/4] iio: adc: ad4000: Use device specific timing for SPI transfers

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Message-ID: <ZzsmUqqyAll9BBCv@debian-BULLSEYE-live-builder-AMD64>
Date: Mon, 18 Nov 2024 08:34:42 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: Marcelo Schmitt <marcelo.schmitt@...log.com>, lars@...afoo.de,
	Michael.Hennerich@...log.com, jic23@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] iio: adc: ad4000: Use device specific timing for SPI
 transfers

On 11/15, David Lechner wrote:
> On 11/14/24 5:51 PM, Marcelo Schmitt wrote:
> > The SPI transfers for AD4020, AD4021, and AD4022 have slightly different
> > timing specifications. Use device specific timing constraints to set SPI
> > transfer parameters.
> > 
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> > ---
> >  drivers/iio/adc/ad4000.c | 50 ++++++++++++++++++++++++++++++++--------
> >  1 file changed, 41 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ad4000.c b/drivers/iio/adc/ad4000.c
> > index 21731c4d31ee..68ac77494263 100644
> > --- a/drivers/iio/adc/ad4000.c
> > +++ b/drivers/iio/adc/ad4000.c
> > @@ -35,10 +35,6 @@
> >  
> >  #define AD4000_SCALE_OPTIONS		2
> >  
> > -#define AD4000_TQUIET1_NS		190
> > -#define AD4000_TQUIET2_NS		60
> > -#define AD4000_TCONV_NS			320
> 
> We are removing 3 but only adding 2 in the struct below?
> 
> If one of these was unused, best to mention it in the commit message.

One of them was unused (AD4000_TQUIET1_NS IRCC).
Sure, will add a comment about it in the commit body.

> 
> > -
> >  #define __AD4000_DIFF_CHANNEL(_sign, _real_bits, _storage_bits, _reg_access)	\
> >  {										\
> >  	.type = IIO_VOLTAGE,							\
> > @@ -122,10 +118,30 @@ static const int ad4000_gains[] = {
> >  	454, 909, 1000, 1900,
> >  };
> >  
> > +struct ad4000_time_spec {
> > +	int t_conv_ns;
> > +	int t_quiet2_ns;
> > +};
> > +
> > +/*
> > + * Same timing specifications for all of AD4000, AD4001, ..., AD4008, AD4010,
> > + * ADAQ4001, and ADAQ4003.
> > + */
> > +static const struct ad4000_time_spec ad4000_t_spec = {
> > +	.t_conv_ns = 320,
> > +	.t_quiet2_ns = 60,
> > +};
> > +
> > +static const struct ad4000_time_spec ad4020_t_spec = {
> > +	.t_conv_ns = 350,
> > +	.t_quiet2_ns = 60,
> > +};
> 
> t_quiet2_ns is the same in both cases, so do we actually need to
> add it here instead of using a common macro? Or if it is for future
> differences, mention that in the commit message.

Okay, will add a macro for setting ad4000_time_spec. My plan is to also add a
t_quiet1_ns filed which will be needed for offloading support.
t_quiet1_ns will also differ between AD4000 and AD4020.